I have little or no experience regarding most DIY projects with cars, because I don't have ramps, lifts, crawlers, etc., and I'm too old and creaky for most of that kind of work, anyway.I think I had asked if during a brake job, does Porsche (or any mechanic) routinely flush/replace brake fluid.
I didn't want to pay for a brake fluid change only to get a brake job a few months later & have it done again.
I bought a tool to check the moisture content of my brake fluid since I live in a dry climate & after 5 years, it is typically still < 1%.
However, I have (and continue to) change brake pads on motorcycles, and never messed with the fluid at the same time. The fluid is a closed system, and moving the calipers out of the way, to work on, replace the pads, etc., doesn't open that system. And -- at other times -- I change the fluid.
So separate projects, separate systems, related only in that the combination of pads and fluid (and master cylinder and calipers) stops the vehicle. I don't see why this would be any different with cars (but I've been wrong before).